About 10 million years into the current Cenozoic Era, or roughly 56 million years ago, during a climate that was hot and wet, two groups of mammals moved from land to water. These were the cetaceans, which include whales, dolphins and porpoises, and the sirenians, with its sea cows, manatees and dugongs.

National Radio Astronomy Observatory -- The National Radio Astronomy Observatory (NRAO) is a research facility of the U.S. National Science Foundation. They provide state-of-the-art radio telescope facilities for use by the scientific community.
They conceive, design, build, operate and maintain radio telescopes used by scientists from around the world. Scientists use their facilities to study virtually all types of astronomical objects known, from planets and comets in our own Solar...

National Solar Observatory -- The National Solar Observatory (NSO) has its primary headquarters in Tucson.
NSO telescopes on Kitt Peak include the McMath-Pierce Solar Telescope Facility containing the world's three largest solar telescopes (1.6-meter main and two 0.9-meter auxiliaries), along with the Vacuum Telescope and the Razdow small solar patrol telescope.
The National Solar Observatory also operates telescopes at Sacramento Peak, New Mexico, that include the Vacuum Tower...

Cerro Tololo Observatory -- astronomical observatory located on Cerro Tololo peak, Chile, with offices in La Serena, about 40 mi (64 km) to the west.
Funded by the U.S. National Science Foundation (NSF), it is operated by the Association of Universities for Research in Astronomy (AURA), which also operates such other major national observatories as the Kitt Peak National Observatory in Arizona.
The principal instrument is a 158-in. (4-m) reflecting telescope, the largest in the...

Kitt Peak Observatory -- astronomical observatory located southwest of Tucson, Ariz.; it was founded in 1958 under contract with the National Science Foundation and is administered by the Association of Universities for Research in Astronomy.
Its principal instrument is the Mayall 158-in. (4-m) reflector. The observatory's equipment also includes 84-in. (2.1 m), 50-in. (1.3-m), 36-in. (0.9-m), and 16-in. (0.4-m) reflecting telescopes as well as a planned 3.5-m telescope.
Used for wide...

Arecibo Observatory -- The Arecibo Observatory is part of the National Astronomy and Ionosphere Center (NAIC), a national research center operated by Cornell University under a cooperative agreement with the National Science Foundation (NSF).
The NSF is an independent federal agency whose aim is to promote scientific and engineering progress in the United States. NSF funds research and education in most fields of science and engineering. Additional support is provided by the National...